Upon an inquiry into the validity of a verdict or indictment, a juror may not testify as to any matter or statement occurring during the course of the jury's deliberations or to the effect of anything upon that or any other juror's mind or emotions as influencing the juror to assent or dissent from the verdict or indictment or concerning the juror's mental processes in connection therewith. Nor may a juror's affidavit or evidence of any statement by the juror concerning a matter about which the juror would be precluded from testifying be received for these purposes.

However, as an exception to this subdivision, a juror may testify and an affidavit or evidence of any kind be received as to any matter or statement concerning only the following questions, whether occurring during the course of the jury's deliberations or not: (1) whether extraneous prejudicial information was improperly brought to the jury's attention; or (2) whether any outside influence was brought to bear upon any juror; or (3) whether any juror has been induced to assent to any general or special verdict, or finding on any question submitted to them by the court, by a resort to the determination of chance.

As I have noted previously, information does not need to appear overtly prejudicial to be considered extraneous prejudicial information for Rule 606(b) purposes, meaning that a dictionary definition of a legal term can be extraneous prejudicial information. Of course, when that (internet) dictionary definition is the same as the legal definition, a juror's use of a dictionary is unlikely to result in a new trial as the recent opinion of the Supreme Court of Montana in Stebner v. Associated Materials, Inc., 2010 WL 2509626 (Mont. 2010), makes clear.

Stebner, the owner of Riverside Apartment Complex, brought a breach of warranty action against Alside. Stebner had made a claim for replacement of the apartment complex's steel siding under [a] Limited Warranty. Alside denied his claim because, according to Alside, the damage to the siding was not covered under the warranty.

A jury trial was held from September 15, 2009, to September 18, 2009. After hearing the evidence, the jury began deliberations at approximately 4:00 p.m. on September 17. Before any deliberations, five jurors voted in favor of Alside, six voted in favor of Stebner, with one abstention. After about an hour of deliberations, the jurors voted six in favor of Stebner and six in favor of Alside. The jury was excused at 5:00 p.m. to allow one juror to pick up a child.

The jury reconvened at 8:30 a.m. the next day. Within five minutes, they voted eleven to one in favor of Alside and delivered the verdict accordingly. After the verdict, Stebner learned from a juror that some of the jurors were allegedly talking about the case outside of the jury room and that one juror had researched the definition of "preponderance" on the internet.

Stebner thus moved for a new trial, but the trial court denied the motion, and Stebner's appeal eventually reached the Supreme Court of Montana. The Montana Supremes found that

a juror affidavit may be used to impeach the verdict if it involves any matter concerning, inter alia, whether extraneous prejudicial information was improperly brought to the jury's attention. M.R. Evid. 606(b)....

In Allers [v. Riley], a bailiff brought a dictionary into the jury room at a juror's request. The dictionary definition of "proximate cause" differed from the court's jury instruction in that it did not include the element of foreseeability....We said that because "the jury used extraneous materials-two dictionaries-to redefine a critical element of this negligence case...Riley's substantial rights were compromised along with his constitutional right to a fair trial ."...

In Brockie v. Omo Constr., 255 Mont. 495, 500, 844 P.2d 61, 61 (1992), the jury foreperson went to the library and conducted research on a theory of physics in hopes of clarifying an expert's testimony. While the foreperson's affidavit stated he did not mention his research during deliberations, two other juror affidavits stated that he did mention his research to the other jurors....We held that the district court abused its discretion when it denied Brockie's motion for a new trial because the foreperson's actions constituted misconduct that prejudiced Brockie....

The Supreme Court of Montana found that the juror's actions in the case before it were like the jurors' actions in Allers and Brockie and that the dictionary definition was thus extraneous prejudicial information and could form the basis for jury impeachment under Montana Rule of Evidence 606(b). But, according to the court, the problem for Stebner was that, unlike in Riley, the (internet) dictionary definition of "preponderance" matched the definition given to jurors during jury instructions, meaning that Stebner was not entitled to a new trial.